Heat exchanger

ABSTRACT

An annular heat exchanger having conically shaped inner and outer walls with a space between said walls occupied by a zig-zag folded strip of material forming several flow ducts. The strip is initially a straight blank that is folded so that the partitions between the ducts extend radially and each partition has the shape of an isosceles trapezium or trapezoid.

United States Patent [191 Meijer et al.

[451 May21, 1974 HEAT EXCHANGER Inventors: Roelf Jan Me'rier; Gregorius Theodorus Maria Neelen; Jules Herman Vree, all of Emmasingel, Eindhoven, Netherlands U.S. Philips Corporation, New York, NY.

Filed: Apr. 21, 1972 Appl. No.: 246,138

Assignee:

Foreign Application Priority Data Apr. 29, 1971 Netherlands 7105840 US. Cl 165/157, 165/167, 432/179 Int. Cl F28d 7/10 Field of Search [65/166, 167, 165, 164,

References Cited UNlTED STATES PATENTS Wunning 432/179 1,636,958 7/1927 Harter.... 165/167 1,636,958 7/1927 Harter 165/167 X 2,566,310 9/1951 Burns et a1 165/140 3,015,475 1/1962 Meiter et a1. [65/141 X FOREIGN PATENTS OR APPLICATIONS 471,475 3/1952 ltaly 165/164 Primary Examiner-Charles J. Myhre Assistant Examiner-Theophil W. Streule, Jr.

Attorney, Agent, or Firm-Frank R. Trifari [57] ABSTRACT 2 Claims, 5 Drawing Figures PATENTEMAY 2 1' m4 saw 1 0F 2 HEAT EXCHANGER BACKGROUND OF THE INVENTION The invention relates to a heat exchanger which is particularly suitable for use as a preheater in a thermodynamic machine and which comprises an inner wall extending according to a plane of revolution and an outer wall situated around said inner wall at a distance and likewise extending according to a plane of revolution; one or more strips of sheet material folded in a zig-zag manner are incorporated in the annular duct formed between said walls and forming partitions between the inner and the outer walls for a number of flow ducts for the heat exchanging media.

A heat exchanger of the above-described type is known from the US. Pat. No. 2,616,530 where a strip of sheet material folded in a zig-zag manner is incorporated between a cylindrical outer wall and a cylindrical inner wall. The strip makes only a line contact with the two walls, which means that the partitions do not extend radially. The result of this is that the ratio of the width of two adjacent flow ducts varies with the radius. This results in the heat transfer between the heat exchanging media being not very favorable. In order for said heat transfer to be as favourable as possible, the ratio of the width of adjacent flow ducts should be the same on any radius, which requires the partitions to extend radially.

A further drawback of the known heat exchanger is that the inner wall and outer wall have a cylindrical shape. This makes mounting and dismantling difficult and hence expensive. As a result of this cleaning of the heat exchanger is also a time-consuming job.

SUMMARY OF THE NEW INVENTION It is the object of the invention to provide a heatexchanger which avoids the above-mentioned drawbacks and is cheap to manufacture. In order to achieve this object the heat exchanger according to the invention is characterized in that the inner wall and the outer wall each extend according to a conical surface and the strips of sheet material are folded so that the partitions extend radially and are alternately connected in pairs by an inner intermediate member which is in contact with the inner wall and an outer intermediate member which is in contact with the outer wall. The partitions mutually have the same dimensions and each has the shape of an isosceles trapezium, the base of which is present on the side of the heat exchanger having the smallest diameter. The outer and inner intermediate members also have the shape of isosceles trapeziums, the bases of which are present on the side of the heat exchanger having the largest diameter. The bases of the outer intermediate members and the bases of the inner intermediate members are in the same relationship to each other as the diameters of the inner and outer walls at that area, the base angles of all the said trapeziums being furthermore equal to each other.

Since in the heat exchanger according to the invention the outer and inner walls are conical, an easy and rapid mounting and dismantling is ensured so that cleaning of said heat exchanger is simple.

As a result of the chosen shape and dimension of partitions and intermediate members, it is possible that the strips of sheet material in the developed condition have a rectangular shape, so that the material in its initial state can be a straight strip, which makes the manufacture cheap. The starting material may be a straight strip which is folded in a particular manner as will be described in greater detail hereinafter with reference to the description of the figures.

In a further favorable embodiment of the heat exchanger according to the invention, the width of the strips which constitute the partitions and intermediate members is larger than the height of the outer and inner walls. In this manner the partitions and intermediate members project beyond said walls on either side, and sealing plates are provided on the end faces of the strips folded in a zig-zag manner. The ducts open into the outer conical surface communicating on the one hand with an inlet and on the other hand with an outlet for one heat exchanging medium, the ducts opening into the inner conical surface communicating with an inlet and an outlet for the other heat exchanging medium.

In this manner an extremely simple communication of the flow duets with the inlets and outlets for the heat exchanging media is obtained, which makes the said heat exchanger cheap. The invention will be described in greater detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWING FIGS. la, b and c are a diagrammatic sectional view, a plan view and an underneath view, respectively, of a heat exchanger,

FIG. 2 shows a straight strip of sheet material provided with folding lines,

FIG. 3 shows diagrammatically the upper part of a thermodynamic machine having a conical preheater present around the burner space.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 in FIG. 1 denotes a conical inner wall and reference numeral 2 denotes a conical outer wall. In the annular duct formed between said wall, a zig-zag folded strip 3 of sheet material is present. The strip 3 is folded so that the partitions 4 extend radially between the flow ducts, the partitions being connected alternately in pairs by an outer intermediate member 5 and an inner intermediate member 6. The outer intermediate members 5 are in contact with the outer wall 2 and the inner intermediate members 6 are in contact with the inner wall 1. The partitions 4 and the outer and inner intermediate members or sides 5 and 6 have the shape of isosceles trapeziums, or trapezoids the bases of the trapeziums which constitute the partitions 4 are situated on the side 7 of the heat exchanger having the smallest diameter, and the bases of the trapeziums which constitute the outer and inner intermediate members are situated on the side 8 having the largest diameter of the heat exchanger.

The transverse dimension of an inner intermediate member is in any place equal to the radius of the inner wall at that area multiplied by 21r divided by the total number of flow ducts, while the transverse dimensions of an outer intermediate member in any place is equal to the radius of the outer wall at that area multiplied by 2w divided by the total number of flow ducts.

The transverse dimension of the partitions 4 is substantially equal to the difference in diameter of the outer and inner walls, the increase of said transverse dimensions from the side 8 to the side 7 exactly corresponding to the decrease of the transverse dimension of the outer and inner intermediate members in the said direction.

By this particular proportioning it is achieved that the developed length of the strip 3 is equally large everywhere so that the heat exchanger can be manufactured from a straight strip 3 i.e. having parallel sides which, as is shown in FIG. 2, can be folded along broken lines which divide the strip into a number of isosceles trapeziums. Since the partitions 4 extend radially, the width ratio of two adjacent flow ducts is the same in any place, which ensures an optimum heat transfer.

FIG. 3 shows diagrammatically the upper part of a.

thermodynamic machine. It comprises mainly a regenerator with which a wreath of heating pipes 16 communicates which open with their other side into an annular duct 17 which communicates with the expansion space 19 of the machine through a wreath of pipes 18 which alternate between the pipes 16. A burner chamber 20 bears on the annular duct 17 to which chamber fuel is supplied via an atomizer 21. A heat exchanger 22 of a construction as shown in FIG. 1 is arranged around the wreath of heater pipes. In this heat exchanger 22, the strip 23 folded in a zig-zag manner projects on either side beyond the conical inner and outer wall 24, 25.

On its lower side, the strip 23 is sealed by a cover plate 26. Bearing on annular ducts 17 is furthermore a conical guiding partition 27 whichon its lower side engages the cover plate 26 in a sealing manner. The heat exchanger furthermore comprises on its inner and outer circumference a layer of an insulating material 28 and 29. Between the layer of insulating material 28 and the guiding partition 27 an annular duct 30 is present which communicates at one end with the burner 20 and at the other end with those flow ducts in heat exchanger 22 which open into the inner conical surface. The flow ducts which open into the outer conical surface on the lower side of the heat exchanger 22 communicate with an annular duct 31 which communicates with the space 32 in which the wreath of heater pipes 16, 18 is arranged.

On the upper side of the heat exchanger 22 the strip 23 is sealed by a cover plate 33, the flow ducts which open into the inner conical surface communicating with an annular duct 34 which is provided with an inlet 35 for air of combustion, the flow ducts which open into the outer conical surface communicating with an annular duct 36 which is provided with an exhaust duct 37 for the combustion gases.

In this construction, the air of combustion follows the path of alternate, primary ducts denoted by solid-line arrows from the inlet 35 through annular duct 34, the flow ducts in heat exchanger 22 opening into the inner conical surface and annular duct 30 to burner 20. As denoted by the brokenline arrows, the combustion gases formed in the burner 20 flow through space 32 to annular duct 31 and thence through the secondary ducts, each of which is intermediate two primary ducts in the heat exchanger 22 opening into the outer conical surface to annular duct 36 and thence to the atmosphere via the exhaust 37.

In this manner, a heat exchanger is obtained which is extremely cheap to manufacture and which can easily be mounted, dismantled and cleaned.

As shown in the drawing, the insulation with minimum volume is readily adapted to the needs, namely at the hot lower side thick at the outside and thin on the inside, and at the comparatively cold upper side just the other way about. The outer dimensions of the heat exchanger in this conception are as small as possible.

We claim:

1. A heat exchanger comprising an outer wall formed as a first conical sleeve with a longitudinal. axis, an inner wall formed as a second conical sleeve secured within the first sleeve with a conical annular space defined between said sleeves, a conical annular member situated within said annular space, this member formed of at least one strip of sheet material, each strip having length and folded along lines transverse to said length in a zig-zag manner to form a plurality of ducts that extend axially relative to said lines and axially in said annular space and are spaced sequentially around said space, said folds comprising a plurality of fold patterns, each pattern providing sequentially an inner section for contacting the inner conical wall, a partition extending generally radially outward, an outer section for contacting the outer conical wall, another partition extending generally radially inward, and another inner section for contacting said inner conical wall, each of said sections and partitions having trapezoidal shape.

2. Apparatus according to claim 1 wherein said ducts comprise alternate primary ducts, and intermediate each two of said primary ducts a secondary duct, the apparatus further comprising first common inlet and outlet means for the primary ducts, and second common inlet and outlet means for the secondary ducts. 

1. A heat exchanger comprising an outer wall formed as a first conical sleeve with a longitudinal axis, an inner wall formed as a second conical sleeve secured within the first sleeve with a conical annular space defined between said sleeves, a conical annular member situated within said annular space, this member formed of at least one strip of sheet material, each strip having length and folded along lines transverse to said length in a zigzag manner to form a plurality of ducts that extend axially relative to said lines and axially in said annular space and are spaced sequentially around said space, said folds comprising A plurality of fold patterns, each pattern providing sequentially an inner section for contacting the inner conical wall, a partition extending generally radially outward, an outer section for contacting the outer conical wall, another partition extending generally radially inward, and another inner section for contacting said inner conical wall, each of said sections and partitions having trapezoidal shape.
 2. Apparatus according to claim 1 wherein said ducts comprise alternate primary ducts, and intermediate each two of said primary ducts a secondary duct, the apparatus further comprising first common inlet and outlet means for the primary ducts, and second common inlet and outlet means for the secondary ducts. 